替换空格

class Solution {
public:
    void replaceSpace(char *str,int length) {
        if(str == NULL || length < 0)return ;
        for(int i=0;i < length;)
        {
            if(str[i] == ‘ ‘)
            {
                length = length + 2;
                int j = length -1;
                while(j > i + 2)
                {
                    str[j] = str[j-2];
                    j--;
                }
                str[i] = ‘%‘;
                str[i+1] = ‘2‘;
                str[i+2] = ‘0‘;
                i = j+1;
            }
            else
                i++;
        }
    }
};

lass Solution {
public:
    void replaceSpace(char *str,int length) {
        if(str == NULL || length < 0)return;
        int i = 0;
        int oldnumber = 0;//记录以前的长度
        int replacenumber = 0;//空格的数目
        while(str[i] != ‘\0‘)
        {
            oldnumber ++;
            if(str[i] == ‘ ‘)
            {
                replacenumber ++;
            }
            i++;
        }
        int newlength = oldnumber + 2 * replacenumber;//插入后的长度
        if(newlength > length)//如果计算后的长度大于总长度就无法插入,说明无空格，不需要插入
        {
            return ;
        }
        int pOldlength = oldnumber;//字符串以‘\0‘结尾
        int pNewlength = newlength;
        while(pOldlength >= 0 && pNewlength>pOldlength)
        {
            if(str[pOldlength] == ‘ ‘)
            {
                str[pNewlength--] = ‘0‘;
                str[pNewlength--] = ‘2‘;
                str[pNewlength--] = ‘%‘;
            }
            else
            {
                str[pNewlength--] = str[pOldlength];
            }
            pOldlength--;//不管是if还是else都要把pOldlength前移
        }
    }
};